Vertical scaling, also known as scaling up, involves increasing the resources of a single server or instance, such as increasing CPU, RAM, or storage capacity. This approach is typically used for applications that have high processing requirements, but may not be as cost-effective in the long run. Horizontal scaling, also known as scaling out, involves adding more servers or instances to distribute the load and increase overall capacity. This approach is often used for applications that have a high number of requests, and can be more cost-effective as it allows for better utilization of resources. Both approaches have their advantages and disadvantages, and the choice between them depends on the specific needs and requirements of the application.